The ctype.h header file of the C Standard Library declares several functions that are useful for testing and mapping characters.
All the functions accepts int as a parameter, whose value must be EOF or representable as an unsigned char.
All the functions return non-zero (true) if the argument c satisfies the condition described, and zero(false) if not.
Library Functions
Following are the functions defined in the header ctype.h −
| Sr.No. | Function & Description |
|---|---|
| 1 | int isalnum(int c)
This function checks whether the passed character is alphanumeric.
|
| 2 | int isalpha(int c)
This function checks whether the passed character is alphabetic.
|
| 3 | int iscntrl(int c)
This function checks whether the passed character is control character.
|
| 4 | int isdigit(int c)
This function checks whether the passed character is decimal digit.
|
| 5 | int isgraph(int c)
This function checks whether the passed character has graphical representation using locale.
|
| 6 | int islower(int c)
This function checks whether the passed character is lowercase letter.
|
| 7 | int isprint(int c)
This function checks whether the passed character is printable.
|
| 8 | int ispunct(int c)
This function checks whether the passed character is a punctuation character.
|
| 9 | int isspace(int c)
This function checks whether the passed character is white-space.
|
| 10 | int isupper(int c)
This function checks whether the passed character is an uppercase letter.
|
| 11 | int isxdigit(int c)
This function checks whether the passed character is a hexadecimal digit.
|
The library also contains two conversion functions that accepts and returns an "int".
| Sr.No. | Function & Description |
|---|---|
| 1 | int tolower(int c)
This function converts uppercase letters to lowercase.
|
| 2 | int toupper(int c)
This function converts lowercase letters to uppercase.
|
Character Classes
| Sr.No. | Character Class & Description |
|---|---|
| 1 |
Digits
This is a set of whole numbers { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 }.
|
| 2 |
Hexadecimal digits
This is the set of { 0 1 2 3 4 5 6 7 8 9 A B C D E F a b c d e f }.
|
| 3 |
Lowercase letters
This is a set of lowercase letters { a b c d e f g h i j k l m n o p q r s t u v w x y z }.
|
| 4 |
Uppercase letters
This is a set of uppercase letters {A B C D E F G H I J K L M N O P Q R S T U V W X Y Z }.
|
| 5 |
Letters
This is a set of lowercase and uppercase letters.
|
| 6 |
Alphanumeric characters
This is a set of Digits, Lowercase letters and Uppercase letters.
|
| 7 |
Punctuation characters
This is a set of ! " # $ % & ' ( ) * + , - . / : ; < = > ? @ [ \ ] ^ _ ` { | } ~
|
| 8 |
Graphical characters
This is a set of Alphanumeric characters and Punctuation characters.
|
| 9 |
Space characters
This is a set of tab, newline, vertical tab, form feed, carriage return, and space.
|
| 10 |
Printable characters
This is a set of Alphanumeric characters, Punctuation characters and Space characters.
|
| 11 |
Control characters
In ASCII, these characters have octal codes 000 through 037, and 177 (DEL).
|
| 12 |
Blank characters
These are spaces and tabs.
|
| 13 |
Alphabetic characters
This is a set of Lowercase letters and Uppercase letters.
|